The Prime Minister was expected formally to start negotiations with other EU member states last week, after Parliament had passed a law allowing talks to begin.

Responding to the announcement, David Davis, the Secretary of State for Exiting the EU, said: “Last June, the people of the UK made the historic decision to leave the EU. Next Wednesday, the Government will deliver on that decision and formally start the process by triggering Article 50.

“We are on the threshold of the most important negotiation for this country for a generation.

“The Government is clear in its aims: a deal that works for every nation and region of the UK and indeed for all of Europe – a new, positive partnership between the UK and our friends and allies in the European Union.”

What is Article 50?

The Lisbon Treaty, which became law in December 2009, is designed to make the EU “more democratic, more transparent and more efficient” and is an agreement signed by the heads of state and governments of countries that are EU members.

How long will it take?

The process is supposed to take two years but many people believe that it could take longer.

The timescale can be extended, but only by the unanimous consent of the European Council. So every other member state Government would have to agree.

Triggering Article 50, formally notifying the intention to withdraw, starts the clock running. After that, the Treaties that govern membership no longer apply to Britain.

The terms of exit will be negotiated between Britain’s 27 counterparts, and each will have a veto over the conditions.

It will also be subject to ratification in national parliaments, meaning, for example, that Belgian MPs could stymie the entire process.

Two vast negotiating teams will be created, far larger than those seen in the British renegotiation. The EU side is likely to be headed by one of the current Commissioners.

Untying Britain from the old membership is the easy bit. Harder would be agreeing a new trading relationship, establishing what tariffs and other barriers to entry are permitted, and agreeing on obligations such as free movement. Such a process, EU leaders claim, could take another five years.

Business leaders want the easiest terms possible, to prevent economic harm. But political leaders say the conditions will be brutal to discourage other states from following suit.

How could the UK create a new life outside of the EU quickly?

One option will be to simply recreate EU laws as British statute. But Civil Service insiders expect a new Brexit government to opt for something much more radical, and to use the opportunity of “throwing off the shackles” to re-regulate Britain.

It means that the Government would have to perform three acts simultaneously:

Negotiate a new deal with Brussels

Win a series of major bilateral trade deals around the world

Revise its own governance as EU law recedes

Running the show would be an effective “Ministry for Brexit”, under a senior minister.

Officials expect the scrapping of EU law could result in an avalanche of new legislation in every corner of Whitehall – perhaps 25 Bills in every Queen’s Speech for a decade.

Hundreds of Treasury lawyers and experts would have to be hired for areas – such as health and safety, financial services and employment – where Britain had lost competence to Brussels. Meanwhile, a Trade Ministry will be required, with hundreds of new negotiators, to establish new deals around the world.